Apataelurus
| Apataelurus Temporal range: early to middle Eocene
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|---|---|
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| Lower jaw of A. kayi | |
Scientific classification 
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| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Mammalia |
| Order: | †Oxyaenodonta |
| Family: | †Oxyaenidae |
| Subfamily: | †Machaeroidinae |
| Genus: | †Apataelurus Scott, 1938 |
| Type species | |
| †Apataelurus kayi Scott, 1938
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| Species | |
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Apataelurus ("false cat") is an extinct genus of saber-toothed hypercarnivorous placental mammals from the extinct family Oxyaenidae, that lived in North America and East Asia from the early to middle Eocene, 48-40 million years ago. This genus was defined by teeth that were well-adapted to a carnivorous diet.[1] A distinct feature described was a long upper canine tooth that resembled a saber tooth. There are two species currently described: Apataelurus kayi, the type species, and Apataelurus pishigouensis, discovered in 1986.
As a large, leopard-sized predator, Apataelurus dominated the Uinta Formation area. It was adapted to taking on large prey with more struggling motion tolerant muscles in its mouth, allowing it to attack large prey that would fight back. It was closely related to other Machaeroidinae, such as Diegoaelurus vanvalkenburghae. Apataelurus and other species within the Uinta Basin emerged during a major transition between the reduction in tropical zones and the increase in temperate and subtropical biomes. Apataelurus was a more evolved member of Oxyaenidae, and lived in the middle to late Lutetian age.
Discovery and naming
[edit]A. kayi was originally discovered by William Berryman Scott in Wagonhound Canyon at the Uinta Formation of the Uinta Basin, Utah.[2] It was described and published in May 1938 as a "problematic, cat-like mandible".[3] The second species, Apataelurus pishigouensis, was discovered at the Hetaoyuan Formation in Henan, China in 1986 by Tong Yongsheng and Lei Yizhen.[4][5]
Description
[edit]Collected Apataelurus specimens consist exclusively of remains of the lower jaw. The most important find is an almost complete lower jaw, which contains part of the rear teeth. Based on the existing dental sockets, a dental formula with two incisors, one canine, four premolars, and two molars was likely present.[6]
The lower jaw was 14.9 cm (5.9 in) long and 2.7 cm (1.1 in) high below the first molar. Towards the front, the horizontal bony body became noticeably higher and ended in the area of the symphysis in a flange-like projection pointing downwards. Such projections are characteristic of predators whose upper canines were significantly elongated, as is the case, for example, in saber-toothed cats. They protected the canine tooth when the jaw was closed. A. pishigouensis and A. kayi share a well developed paraconid that is almost as developed as the talonoid.[7][8]
The ascending ramus featured a deep masseteric fossa with sharp edges to which the masseter muscle attached. The coronoid process was significantly reduced in size. The articular process, which ended below the dental plane, was also much smaller. The entire lower jaw reached a height of 1.8 cm (0.71 in). Both the protrusion of the anterior segment of the mandible and the low position of the coronoid process were more pronounced in Apataelurus than in the closely related Machaeroides.[9]
Classification
[edit]Apataelurus is a genus from the extinct subfamily Machaeroidinae, within the extinct order Oxyaenidae, which is also in the extinct order Oxyaenodonta. According to phylogenetic studies, the clade Pan-Carnivora is split into two orders: Oxyaenodonta and Hyaenodonta.[10]
Three Oxyaenid genera and four species have thus far been described: Machaeroides, with species M. simpsoni and M. eothen, Apataelurus, and Diegoaelurus.[11] Of the three genera, Machaeroides is the most primitive, with very few adaptations to the saber tooth dental form. Apataelurus and Diegoaelurus are similarly evolved, slightly more derived from M. eothen.[12] However, Diegoaelurus differed with its shorter mandibular flange, suggesting a more specialized carnivorous diet.[4]
| Machaeroidinae |
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The cladogram above shows the divergence of the three genera.[12]
Paleobiology
[edit]
Due to the lack of specimens, there is little information about its paleobiology and behavior. Its detention and similarity to other "creodonts" and Machaeroides suggests that it had a carnivorous diet.[12] Relying on relative jaw size, A. kayi was approximately the size of a leopard. It was significantly larger than Diegoaelurus, a similar Oxyaenid predator. It likely hunted large prey, including uintatheres and brontotheriid perissodactyls. A. pishigouensis, which lived in now-China, likely hunted perissodactyls related to modern-day tapirs.[13]
The mandible of A. kayi is less dorsoventrally buttressed (a bodily structure reinforced from the top to the bottom) than the two Machaeroides species. This difference could indicate that small Machaeroidinae fed on smaller prey, while Apataelurus preferred larger prey. Due to the fact that Machaeroidinae had more dorsoventrally buttressed mandibles, it is likely that they were more adapted to dealing with smaller prey that inflicted less torsional stress (side to side or twisting motions). A. kyai's mandible could have been less buttressed to allow for more torsion resistant motion when dealing with larger and stronger prey. A. kayi had 89% of the bite force of Panthera pardus, a contemporary predatory mammal with similar mandibular length.[14]
Paleoecology
[edit]Apataelurus lived in a warm and humid climate, characterized by fluvial and floodplain environments. The Uinta Formation in this area comprises an interbedded sequence of silt, clay, and small amounts of gravel.[15] The Uinta Basin was formed in the very Late Cretaceous during the Laramide uplift of the Uinta Mountains. This formation, alongside the Green River and Piceance Creek basins, began forming during the Laramide orogeny. The Laramide orogeny was a period of great tectonism in North America that began in the Late Cretaceous and continued until the late Eocene.[16]
The Uinta Formation
[edit]
The Uinta Formation is notable for its vast deposits of fossil mammals, which would come to define the Uintan Stage of the North American Land Mammal Age (NALMA). The Uinta Formation has been formally divided into a lower Wagonhound Member, where Apataelurus was discovered, and an upper Myton Member (named for the nearby town of Myton).[17] Despite this formal classification, geologists and paleontologists organize the formation into three components: Uinta A, B, and C. These are ordered from lowest (oldest) to highest. Uinta A and B comprise of Wagonhound Canyon and the areas nearby, while C represents the Myton Member.[18] Based on the presence of Uintian brontotheres, Uinta A is post-Bridgerian.[19]
Mammalian biostratigraphy
[edit]The Uintan NAMLA was a major transition in mammalian evolution, as approximately 31% of modern mammalian families appear in the fossil record. The Uintan NAMLA was the end of a global greenhouse that had begun in the early Eocene. Tropical and rainforest biomes started to decrease, and subtropical and temperate habitats began to appear.[17] Primitive perissodactyls were replaced with perissodactyls more adapted to the subtropical conditions. Furthermore, rabbits made their first appearance alongside small rodents such as Paramys (Rodentia) and the genus Honrovits (Chiroptera).[20]
The vast majority of mammalian fossils are found within the B1, B2 and C areas, and include the following species:
| Species | Uinta B1 | Uinta B2 | Uinta C |
|---|---|---|---|
| Achaenodon uintensis | Present | ||
| Protoreodon parvus | Present | ||
| Oromeryx plicatus | Present | ||
| Harp agolestes | Present | ||
| Eomoropus amarorum | Present | Present | |
| Hyrachyus eximius | Present | Present | |
| Amynodon reedi | Present | ||
| Eobasileus cornutus | Present | ||
| Limnocyon potens | Present | ||
| Mesonyx obtusidens | Present | ||
| Metarhinus fluviatalis | Present | ||
| Pantolestes longicaudus | Present | ||
| Sciuravus popi | Present | ||
| Uintatherium anceps | Present | ||
| Auxontodon | Present | ||
| Colodon | Present | ||
| Duchesneodus | Present | ||
| Eosictis | Present | ||
| Janimus | Present |
The Eocene Uinta ecosystem
[edit]Apataelurus was likely near the top of the food chain, with hypercarnivorous adaptations and size advantages over other Oxyaenodonts. The Uinta Formation was dominated by perissodactyls such as Dolichorhinus, Metarhinus, and Sthenodectes.[21] In addition to perissodactyls, artiodactyls such as the pig-like Achaenodon inhabited the area. In lakes, rivers, and other fast moving waterways, Priscacara was likely present, a temperate bass found in Lake Uinta and Lake Gossiute, Wyoming.[22]
Temporal distribution within Oxyaenidae
[edit]Apataelurus is predominantly featured in the late middle Eocene, particularly in the Lutetian.[23]
References
[edit]- ^ "PBDB Taxon". paleobiodb.org. Retrieved 1 June 2025.
- ^ "PBDB Taxon". paleobiodb.org. Retrieved 1 June 2025.
- ^ Scott, William Berryman; Scott, William Berryman (6 May 1938). "A problematical cat-like mandible from the Uinta Eocene, Apataelurus kayi Scott". Annals of the Carnegie Museum. 27: 113––120. Bibcode:1938AnCM...27..113S. doi:10.5962/p.226703.
- ^ a b Werdelin, Lars (2024). "Hypercanines: Not just for sabertooths". The Anatomical Record. n/a (n/a). doi:10.1002/ar.25510. ISSN 1932-8494.
- ^ Yongsheng, Lei Yizhen (1986). "Fossil creodonts and carnivores (Mammalia) from the Hetaoyuan Eocene of Henan". Vertebrata PalAsiatica. 24: 210–221.
- ^ "Morphobank". morphobank.org. Retrieved 1 June 2025.
- ^ "Metering | MorphoBank". morphobank.org. Retrieved 2 June 2025.
- ^ Solé, Floréal; Ladevèze, Sandrine (2017). "Evolution of the hypercarnivorous dentition in mammals (Metatheria, Eutheria) and its bearing on the development of tribosphenic molars". Evolution & Development. 19 (2): 56–68. doi:10.1111/ede.12219. ISSN 1525-142X.
- ^ Zack, Shawn P. (22 November 2019). "The first North American Propterodon (Hyaenodonta: Hyaenodontidae), a new species from the late Uintan of Utah". PeerJ. 7: e8136. doi:10.7717/peerj.8136. ISSN 2167-8359. PMC 6876642. PMID 31772846.
- ^ "Ferae Linnaeus, 1758". www.gbif.org. Retrieved 1 June 2025.
- ^ "New Sabre-tooth Predator Precedes Cats by Millions of Years". www.sdnhm.org. Retrieved 1 June 2025.
- ^ a b c Zack, Shawn P.; Poust, Ashley W.; Wagner, Hugh (2022). "Diegoaelurus, a new machaeroidine (Oxyaenidae) from the Santiago Formation (late Uintan) of southern California and the relationships of Machaeroidinae, the oldest group of sabertooth mammals". PeerJ. 10: e13032. doi:10.7717/peerj.13032. ISSN 2167-8359. PMC 8932314. PMID 35310159.
- ^ "One of the earliest sabre-toothed mammals discovered in the USA | Natural History Museum". www.nhm.ac.uk. Retrieved 2 June 2025.
- ^ Therrien, Francois (April 2005). "Feeding behaviour and bite force of sabretoothed predators". Zoological Journal of the Linnean Society.
- ^ "BLOG: Earliest Uintan Mammals". Palaeontologia Electronica. Retrieved 2 June 2025.
- ^ Rogers, James (28 November 1977). "Report of Investigation No. 122: Utah Geological and Mineral Survey" (PDF). Preliminary Geologic Reconnaissance of Twelve Proposed Coal-Fired Power Plant Sites.
- ^ a b c Murphey, Townsend, Friscia, Evanoff (2011). "Paleontology and stratigraphy of middle Eocene rock units in the Bridger and Uinta Basins, Wyoming and Utah". The Geological Society of America (Field Guide 21): 132–168.
{{cite journal}}: CS1 maint: multiple names: authors list (link) - ^ Townsend, K. E.; Friscia, A. R.; Rasmussen, D. T. (2006). "Stratigraphic Distribution of Upper Middle Eocene Fossil Vertebrate Localities in the Eastern Uinta Basin, Utah, with Comments on Uintan Biostratigraphy". The Mountain Geologist. 43 (2): 115–134.
- ^ "Abstract: THE FAUNA AND AGE OF THE UINTA "A," UINTA FORMATION (MIDDLE EOCENE), NORTHEASTERN UTAH, USA (Rocky Mountain (63rd Annual) and Cordilleran (107th Annual) Joint Meeting (18–20 May 2011) )". gsa.confex.com. Retrieved 2 June 2025.
- ^ "Mindat.org". www.mindat.org. Retrieved 1 June 2025.
- ^ Burger, Benjamin J. "THE SYSTEMATIC POSITION OF THE SABER-TOOTHED AND HORNED GIANTS OF THE EOCENE: THE UINTATHERES (ORDER DINOCERATA)" (PDF). Utah State University Uintah Basin Campus.
- ^ "Diplomystus Cope, 1877". www.gbif.org. Retrieved 2 June 2025.
- ^ Janis, Christine M.; Scott, Kathleen M.; Jacobs, Louis L. (28 May 1998). Evolution of Tertiary Mammals of North America: Volume 1, Terrestrial Carnivores, Ungulates, and Ungulate Like Mammals. Cambridge University Press. ISBN 978-0-521-35519-3.