Diegoaelurus

Diegoaelurus Temporal range: Middle Eocene (Uintan) 43–42  Ma PreꞒ Ꞓ O S D C P T J K Pg N ↓
Holotype of Diegoaelurus vanvalkenburghae, (SDSNH 38343)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	† Oxyaenodonta
Family:	† Oxyaenidae
Subfamily:	† Machaeroidinae
Genus:	† Diegoaelurus Zack, Poust, & Wagner, 2022
Type species
Diegoaelurus vanvalkenburghae Zack, Poust, & Wagner, 2022
A map showing the fossil finds of D. vanvalkenburghae as well as other machaeroidinid genera.

Diegoaelurus ("San Diego's cat") is an extinct genus of placental mammals from the extinct subfamily Machaeroidinae within extinct family Oxyaenidae. This genus contains only one species Diegoaelurus vanvalkenburghae, which was found in the Santiago Formation in California. This mammal lived during the Uintan stage of the Middle Eocene Epoch around 43 to 42 million years ago. ^{[1] [2]}

Etymology

The name of genus Diegoaelurus comes from city San Diego and from Ancient Greek αἴλουρος (aílouros-) ' cat '. Diegoaelurus vanvalkenburghae was named after Dr. Blaire Van Valkenburgh in honor of her research on carnivorous mammals and saber-toothed predator paleoecology. ^[1]

Discovery

The holotype fossils were discovered in Oceanside, San Diego county by paleontologist Brad Riney in 1988. ^[1] The fossils were housed for over three decades in a museum until 2022 when the fossils were described and recognised as a new genus and species. ^{[1] [3]} This creature is so far the only North American species of Machaeroidinae known outside of Utah and Wyoming. ^[1] According to a paper on the creature, ''The present study highlights how poorly documented the machaeroidine fossil record remains''. ^[1]

Description

A radiograph showing a missing tooth in SDSNH 38343, the paper has noted that this could be pathological or it could have happened well antemortem.

Diegoaelurus vanvalkenburghae was small in stature, with a size comparable to a fossa. ^[3] The holotype fossils (SDSNH 38343) consists of a mandible and well preserved dentition. ^[1] Its discovery has made paleontologists question whether this group's extinction was caused due to the large faunal turnover during the transitional period between middle and late Eocene. ^[1] This creature as well as its subfamily were some of the first predatory saber toothed mammals to have evolved, 30 million years before the Machairodontinae (saber-toothed cats) evolved in the Miocene. ^{[1] [4]} Due to the lack of remains, there is questioning to these animals ecological niches. ^[1] However, there are good remains from Machaeroides eothen which support a hypercarnivorous lifestyle for the group. ^[1] D. vanvalkenburghae was one of the last surviving members of its subfamily. ^[1]

Classification

The phylogenetic relationships of genus Diegoaelurus are shown in the following cladogram: ^[1]

Machaeroidinae	Machaeroides simpsoni Machaeroides eothen Diegoaelurus vanvalkenburghae Apataelurus pishigouensis Apataelurus kayi

Extinction

Diegoaelurus along with all the members of its subfamily in the middle Eocene, which may be linked to the significant faunal overturn during the transition period between the middle and late Eocene. ^[1] Some argued the cause of their extinction was due to potential competition with nimravids, ^[1] other experts don’t agree with competitive replacement being the cause of the extinction of the machaeroidines, ^{[5] [6]} as excellent fossil record of North America indicates the decline of oxyaenids were declining before the appearance of the replacement taxa such as nimravids. ^[5] In addition, the youngest records of machaeroidines predate the oldest records of nimravids. ^{[1] [7]}

Instead, their extinction was likely due to the changing climate. ^{[6] [5]} During the last 10 million years of the Eocene (43 to 33 Ma), the planet transitioned from a warm moist tropical to a cooler, seasonally arid world. ^[5] Because of their low mobility as well as preference for closed habitats, oxyaenids couldn’t adapt to the more open, temperate forests. ^{[6] [1]} Once oxyaenids went extinct, their ecological niche was filled in by the nimravids, a family of saber-toothed mammals that belonged to the group Feliformia, as well as hyaenodonts, amphicyonids, and early canids. ^{[1] [8] [9] [5] [7]}

References

1. Zack, Shawn P.; Poust, Ashley W.; Wagner, Hugh (2022-03-15). "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.
2. Sofia Quaglia (March 15, 2022). "A new saber-toothed mammal was among the first hypercarnivores". Science News.
3. "Paleontologists discover new San Diego saber-toothed catlike species". Los Angeles Times. 2022.
4. "Not all saber-toothed animals were predators, fossils reveal". National Geographic . 2020. Archived from the original on March 3, 2021.
5. Van, Valkenburgh B. (1999). "Major patterns in the history of carnivorous mammals". Annual Review of Earth and Planetary Sciences. 27: 463–493. Bibcode:1999AREPS..27..463V. doi:10.1146/annurev.earth.27.1.463.
6. Kort, Anne E. (2019). "The Paleoecology of Patriofelis ulta and Implications for Oxyaenid Extinction (thesis)". Indiana University .
7. Poust, Ashley; Barrett, Paul Z.; Tomiya, Susumu (2022). "An early nimravid from California and the rise of hypercarnivorous mammals after the middle Eocene climatic optimum". Biology Letters. 18 (10): 333–347. doi:10.1098/rsbl.2022.0291. hdl: 2433/276689 . PMC   9554728 . S2CID   252818430.
8. Diegoaelurus in the Paleobiology Database
9. Werdelin, L.; Yamaguchi, N.; Johnson, W. E. & O'Brien, S. J. (2010). "Phylogeny and evolution of cats (Felidae)". In Macdonald, D. W. & Loveridge, A. J. (eds.). Biology and Conservation of Wild Felids. Oxford, UK: Oxford University Press. pp. 59–82. ISBN   978-0-19-923445-5.