Hoplophoneus

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Hoplophoneus
Temporal range: Late Eocene to Early Oligocene (Chadronian to Arikareean) 35.7–30.5  Ma
Hoplophoneus primevus IMG 4443.jpg
H. primaevus skeleton, Zurich natural history museum
Scientific classification OOjs UI icon edit-ltr.svg
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family:† Nimravidae
Subfamily:† Hoplophoninae
Genus:† Hoplophoneus
Cope, 1874
Type species
Hoplophoneus primaevus
Leidy, 1851
Other Species
  • H. oharrai (Jepsen, 1926)
  • H. occidentalis (Leidy, 1866)
Synonyms

H. occidentalis

  • Dinotomius atroxWilliston, 1895
  • Drepanodon occidentalis Leidy, 1866
  • Machairodus occidentalis Leidy, 1866

H. primaevus

  • Hoplophoneus mentalis Sinclair, 1921
  • Hoplophoneus oreodontisCope, 1874

Hoplophoneus (Greek: "murder" (phonos), "weapon" (hoplo) [1] ) is an extinct genus of the family Nimravidae, sometimes known as false saber-toothed cats. It's a member of the subfamily known as Hoplophoninae, closely related to nimravids such as Eusmilus and Nanosmilus . Hoplophoneus lived in North America and Asia during the Late Eocene to Early Oligocene epochs from 35.7 to 30.5 mya, existing for approximately 5.2 million years. [2] [3] Including supplementary materials The genus currently consists of three named species: H. oharri, H. occidentalis, and H. primaveus.

Contents

Taxonomy

H. strigidens was considered nomen dubium by Bryant in 1996. [4] In 2000, an unnamed species of Hoplophoneus was found within late Eocene rocks of Thailand. [5]

In 2016, all North American species of Eusmilus were placed in Hoplophoneus by Paul Z. Barrett. In addition, it was found that H. mentalis was a junior synonym of H. primaevus. [6] However, in 2021, Barret revised this phylogeny. His phylogenetic analysis suggests H. cerebralis, H. dakotensis, and H. sicarius were actually species of Eusmilus instead of Hoplophoneus. [3] A 2025 study recovered Hoplophoenus as paraphyletic genus. [7]

Description

H. occidentalis skull Hoplophoneus occidentalis skull.jpg
H. occidentalis skull

Hoplophoneus, though not a true felid, was similar to cats in outward appearance. Hoplophoneus showed adaptations of high specialization, such as the development of its canines and mandibular flange and overall robustness of its build. The humerus of Hoplophoneus showed prominent areas for insertion of deltoid and supinatory muscles, resembling that of later barbourofelins and thylacosmilids. [8] H. primaevus is estimated to have weighed 15–19.5 kg (33–43 lb) and stood 48 cm (1 ft 7 in) at the shoulders. [9] [10] [8] H. occidentalis was significantly larger than H. primaevus, standing 60 cm (2 ft 0 in). [11] While Sorkin, in his 2008 study, estimated the species could've weighed 160 kg (350 lb), similar to a large jaguar. [12] Other experts suggested a smaller size. Turner suggested H. occidentalis was about the size of a large leopard. [13] Based on a sample size of 8 specimens, Meachen found that the species weighed 65 kg (140 lb). [10] This species was also found to have been sexually dimorphic. [14]

Paleobiology

Brain anatomy

The posterior vermis of the cerebellum was found to be straight, although the overlap of the cerebellum by the cerebrum was smaller than extant felids. It was also found that the olfactory bulbs were relatively small in Hoplophoneus. [15] Despite this, H. primaevus was found have an encephalization quotient score of 0.36-0.37. This EQ score is similar to that of cougars, and scoring higher than jaguars. [16]

Predatory behavior

Hoplophoneus was found to have humeri as robust and deltopectoral crests as long as Oxyaeninae and Borhyaenoidea. This suggests much like oxyaenines and borhyaenoids, Hoplophoneus possessed a more robust humeri than any felid. [12] Due to the presence of robust bones and large areas of muscle attachments, Meachen speculated that H. occidentalis showed specialization for large prey. [10] Lautenschlager et al. 2020 estimated the jaw gape for this species to be around 98.22°. In addition, H. oharri and H. primaveus had a jaw gape of 97° and 95° respectively. They argue due to the wide jaw gape of over 90°, combined with little bending strength values over time suggests they have an intermediate killing strategy towards large prey. [17] Including supplementary materials

However, Anderson et al. 2011 found that increased jaw gape and canine size has a great impact on small to medium sized prey, but little impact on large prey. Based on their analysis, they argue the adaptation of sabertoothed predators was killing normal sized prey faster than their nonsabertooth counterparts. [18] Elbow morphology recovered Hoplophoneus as an ambush predator. [19]

Pathology

An adult specimen of H. primaevus discovered in Badlands National Park, South Dakota, in 2010 by paleontologist Clint Boyd et al. was found to have bite marks on its skull from the teeth of another adult individual of Hoplophoneus. From examination of the wounds, it was found that the animal had been wounded by its rival's saber-teeth. Regrowth of bone around the injuries shows that the nimravid survived the attack. Similar finds also reveal that such fights were likely common among nimravids and that they would often aim for the back of the skulls and eyes of their opponents. [20]

Paleoecology

Life restoration by Charles R. Knight, 1897 Hoplophoneus by Knight.jpg
Life restoration by Charles R. Knight, 1897

H. occidentalis roamed North America from the late Eocene to early Oligocene from 33.4 to 31.4 mya, found in states such as Nebraska, North Dakota, South Dakota, and Wyoming. [3] Including supplementary materials Within the Oreodon layer of the Brule Formation in South Dakota, it coexisted with predators such as fellow nimravid H. primaevus, the amphicyonid Daphoenus , entelodontidae Archaeotherium mortoni , hyaenodont Hyaenodon . Contemporary herbivores such the camel Poebrotherium wilsoni , the horse Mesohippus bairdi , tapirs such as Protapirussimplex and Colodon occidentalis , the hypertragulid Hypertragulus calcaratus and hornless rhinos such as the hyracodontid Hyracodon and Subhyracodon . [21]

H. primaevus also roamed North America from the late Eocene to early Oligocene, from 35.7 to 30.58 mya, found in states such as Nebraska, South Dakota, Colorado, Wyoming, and Oregon. [3] Including supplementary materials Within Chadron in Place, it coexisted with predators such as the nimravid Dinictis and canid Hesperocyon gregarius . [22]

It was believed to have been the dominant cat-like predator, with its only serious competitor being the larger hyaenodonts like Hyaenodon. [23]

References

  1. ↑ "Glossary. American Museum of Natural History". Archived from the original on 20 November 2021.
  2. ↑ Turner, Alan. National Geographic Prehistoric Mammals. National Geographic, 2004., pp.120-121
  3. 1 2 3 4 Barrett, Paul Zachary (26 October 2021). "The largest hoplophonine and a complex new hypothesis of nimravid evolution". Scientific Reports. 11 (1) 21078. Bibcode:2021NatSR..1121078B. doi: 10.1038/s41598-021-00521-1 . PMC   8548586 . PMID   34702935. S2CID   240000358.
  4. ↑ Prothero, DR; Emry, RJ; Bryant, HN (1996). "Nimravidae". The Terrestrial Eocene-Oligocene Transition in North America. pp. 453–475.
  5. ↑ Peigné, Stéphane; Chaimanee, Yaowalak; Jacques, J. J; Suteethorn, Varavudh; Ducrocq, Stéphane (March 2000). "New Eocene nimravid carnivoran from Thailand" . Journal of Vertebrate Paleontology. 20 (1): 157–163. doi:10.1671/0272-4634(2000)020[0157:ENCFT]2.0.CO;2.
  6. ↑ Barrett PZ. (2016) Taxonomic and systematic revisions to the North American Nimravidae (Mammalia, Carnivora) PeerJ 4:e1658 https://doi.org/10.7717/peerj.1658
  7. ↑ Chabrol, Nils; Morlon, Hélène; Barido-Sottani, Joëlle (July 2025). "The Fossilized Birth Death Process with heterogeneous diversification rates unravels the link between diversification and specialisation to a carnivorous diet in Nimravidae (Carnivoraformes)". bioRxiv: 1–26. doi:10.1101/2025.07.15.664897.
  8. 1 2 Turner, Alan (1997). The Big Cats and their Fossil Relatives: an illustrated guide . New York: Columbia University Press. p. 25. ISBN   978-0-231-10228-5.
  9. ↑ Dubied, Morgane; Solé, Floréal; Mennecart, Bastien (29 July 2019). "The cranium of Proviverra typica (Mammalia, Hyaenodonta) and its impact on hyaenodont phylogeny and endocranial evolution". Palaeontology. 62 (6): 983–1001. Bibcode:2019Palgy..62..983D. doi: 10.1111/pala.12437 .
  10. 1 2 3 Meachen, J. A. (2012). "Morphological convergence of the prey-killing arsenal of sabertooth predators". Paleobiology. 38 (1): 1–14. doi:10.1666/10036.1. JSTOR   41432156.
  11. ↑ Antón, Mauricio (2013). Sabertooth. Bloomington, Indiana: University of Indiana Press. p. 95. ISBN   978-0-253-01042-1.
  12. 1 2 Sorkin, B. (2008-04-10). "A biomechanical constraint on body mass in terrestrial mammalian predators". Lethaia. 41 (4): 333–347. Bibcode:2008Letha..41..333S. doi:10.1111/j.1502-3931.2007.00091.x.
  13. ↑ Turner, Alan (1997). The Big Cats and their Fossil Relatives: an illustrated guide . New York: Columbia University Press. pp.  234. ISBN   978-0-231-10228-5.
  14. ↑ Turner, Alan (1997). The Big Cats and their Fossil Relatives: an illustrated guide . New York: Columbia University Press. p. 93. ISBN   978-0-231-10228-5.
  15. ↑ Lyras, George A.; Geer der van, Alexandra Anna; Werdelin, Lars (November 2022). "Paleoneurology of Carnivora". Paleoneurology of Amniotes, New Directions in the Study of Fossil Endocasts. pp. 681–710. doi:10.1007/978-3-031-13983-3_17. ISBN   978-3-031-13982-6.
  16. ↑ Dubied, Morgane; Solé, Floréal; Mennecart, Bastien (29 July 2019). "The cranium of Proviverra typica (Mammalia, Hyaenodonta) and its impact on hyaenodont phylogeny and endocranial evolution". Palaeontology. 62 (6): 983–1001. Bibcode:2019Palgy..62..983D. doi: 10.1111/pala.12437 .
  17. ↑ Lautenschlager, Stephan; Figueirido, Borja; Cashmore, Daniel D.; Bendel, Eva-Maria; Stubbs, Thomas L. (2020). "Morphological convergence obscures functional diversity in sabre-toothed carnivores". Proceedings of the Royal Society B . 287 (1935): 1–10. doi: 10.1098/rspb.2020.1818 . ISSN   1471-2954. PMC   7542828 . PMID   32993469.
  18. ↑ Andersson, K.; Norman, D.; Werdelin, L. (2011). "Sabretoothed carnivores and the killing of large prey". PLOS ONE. 6 (10) e24971. Bibcode:2011PLoSO...624971A. doi: 10.1371/journal.pone.0024971 . PMC   3198467 . PMID   22039403. Open Access logo PLoS transparent.svg
  19. ↑ Castellanos, Miguel (2024). Hunting Types in North American Eocene and Oligocene Carnivores and Implications for Nimravid Extinction (Graduate Research Thesis & Disserations)
  20. ↑ The Dakota Badlands Used to Host Sabertoothed Pseudo-Cat Battles
  21. ↑ PaleoBiology Database: Brule Formation
  22. ↑ PaleoBiology Database: Chadron in Place
  23. ↑ Antón, Mauricio (2013). Sabertooth. Bloomington, Indiana: University of Indiana Press. p. 48. ISBN   978-0-253-01042-1.
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